Coffee extract is brewed by contacting the roasted or ground coffee with boiling or near-boiling water for a predetermined brewing time. The extract, including the solutes, is then separated from the insolubles to obtain the resulting beverage which is promptly consumed. However, in this day and age where there is a significant trend towards convenience foods, the use of instant coffees is preferred by a segment of coffee consumers.
Instant coffee is basically the dried water-extract of roasted, ground coffee. The beans used to make instant coffee are blended, roasted and ground as they are in the making of regular coffee. In order to make instant coffee, the roasted, ground coffee is then charged into columns called percolators through which hot water is pumped, resulting in a concentrated coffee extract. The extract is then dried, usually by either spray drying or freeze drying, to produce the final coffee powder which is sold to the consumer. Upon the addition of hot water to the dried coffee powder, coffee is obtained without the need to go through the usual and more complicated brewing steps.
As is explained in Canadian Patent No. 670,794 (to Standard Brands Incorporated), spray-dried instant coffee consists of hollow spheres or aggregates thereof which form a fine and persistent foam when hot water is added to the coffee powder. This is in contrast to the coarser and more quickly subsiding foam which is formed when a hot water-extract of ground roasted coffee is poured into a cup. Consequently, because typically brewed coffee does not have such a foam, the foam produced by the spray-dried instant coffee is undesirable. Accordingly, many techniques have been developed to reduce, alter or eliminate the foaming characteristics of spray-dried instant coffee. For example, in Canadian Patent No. 670,794, a small amount of a monoglyceride of a higher fatty acid is incorporated in the spray-dried coffee to change the appearance of the foam produced when the coffee is contacted with hot water. The new foam has the characteristics of the foam in a cup of brewed coffee rather than the more persistent fine foam normally associated with spray-dried instant coffee.
On the other hand, the production of foam on coffee is not always undesirable. In particular, espresso coffee is a special coffee beverage type that is winning increased approval with the consumer. Espresso coffee typically comprises finely milled roasted beans which are brewed rapidly with pressurized water/steam which coincidentally results in the formation of in-cup foam. The resulting espresso beverage provides body and flavor aspects very distinct from the normal cup of coffee. Espresso is said to have a dark, rich flavor and appearance and is accompanied by a head of lighter-colored froth or foam which espresso beverage devotees consider crucial. The foam contains colloidal oil droplets and solid particles which give the espresso its characteristic texture and mouth feel. It is to be noted that the froth or foam characteristic of espresso coffee is not at all similar to the foam formed from the spray-dried instant coffee described above.
As would be expected, due to its unique flavor and other characteristics, espresso coffee is not easily made. In order to produce a consistently high-quality espresso beverage, the brewing process must be controlled very closely, i.e., a very short brewing time, specific pressures, temperatures, volumes of water delivered to the ground coffee, the need for precise adjustments, etc. Consequently, espresso brewing machines are relatively complicated, large and expensive and require a certain amount of skill to operate. Accordingly, it would be preferable to find an alternative method for providing an espresso beverage, one which is simpler and easier to employ.
Although the flavor of espresso coffee may be mimicked by the use of dark roast Arabicas and extraction processing conditions, the foaming characteristics of espresso are not easily replicated as the foaming of roasted and ground espresso is primarily induced by high-pressure steam which is provided by an espresso machine. The high-pressure steam provides a source of sparging gas, which, with the aid of surface-active species present in the coffee, form foam cells. Espresso brewing also results in the emulsification of oil into the brew and the foam. The resultant foam consists of water, gas, surface-active species and oil, and has a creamy appearance and texture.
It is widely accepted that the protein present in unroasted coffee beans is not retained in roasted coffee or in soluble coffee powders produced from extracts of roasted coffee. Coffee protein is rapidly and substantially denatured and degraded by the high temperatures and chemical reactions that occur during roasting and extracting. See, for example, Coffee, Volume 1: Chemistry, R. J. Clarke and R. Macrae, Eds., Elsevier Applied Science Publishers, New York, 1987, pp. 138-143. As reported in Coffee, Recent Developments, R. J. Clarke and O. G. Vitzthum, Eds., Blackwell Science Ltd, London, 2001, p. 155, coffee beverages contain “transformed proteic material grouped under the broad name of melanoidins”. Accordingly, soluble coffee powders, including soluble espresso powders, produced from roasted coffee are regarded as being devoid of protein. Unlike typical food foams, which are stabilized by proteins such as occur in milk, eggs, wheat, and the like, it is believed that carbohydrates, particularly coffee polysaccharides, stabilize espresso foam. As also reported in Coffee, Recent Developments, p. 15, the stability of espresso foams is directly related to the concentration of polysaccharide present and the foam stabilizing effect is attributed to viscosity imparted to the extract by galactomannan.
U.S. Pat. No. 5,882,717 to Panesar et al., incorporated herein by reference, discloses a method for making a spray-dried instant coffee using a process of foaming a coffee extract by gas injection followed by homogenizing the foamed coffee extract to reduce gas bubble size and then subsequently spray drying the homogenized extract to produce a soluble espresso coffee powder having voids formed by gas bubbles. As a result, the resulting entrapped gas bubbles at atmospheric pressure are provided by gas dispersed in a liquid extract prior to spray drying.
U.S. Pat. No. 6,713,113, incorporated herein by reference, discloses a powdered soluble foaming ingredient which has a matrix containing a carbohydrate, a protein and entrapped pressurized gas. The gas is released upon addition of the dry powder to liquid.
U.S. Pat. No. 6,953,592, incorporated herein by reference, discloses a method for forming tablets or powders of carbohydrate-based pharmaceuticals or foods which includes subjecting tablets or powders which comprise a beverage base such as soluble coffee, foamed powder, sugar and creamer to pressure and temperature to produce a tablet or powder with increased solubility or dispersability on contact with water. In addition, a method is disclosed which promotes the dissolution or dispersion of a tablet or non-foaming powder by subjecting the tablet or powder to pressurized gas so that gas is entrapped therein to promote dissolution or dispersion of the tablet or powder on contact with water. Improved dissolution of carbohydrate-based tablets comprised of spray-dried coffee and either carbohydrate crystalline sucrose or foamed carbohydrate powder and spray-dried creamer powder containing entrapped gas is demonstrated in working examples therein. However, U.S. Pat. No. 6,953,592 does not demonstrate in any working examples of manufacturing a foaming soluble coffee powder or foaming soluble espresso powder containing entrapped pressurized gas therein. Further, improved dissolution or dispersability of a coffee powder, alone or in combination with other ingredients, containing entrapped gas is not demonstrated in any working example therein.
U.S. Pat. Nos. 4,830,869 and 4,903,585, both to Wimmers, et al., incorporated herein by reference, disclose a method for making a coffee beverage having a thick layer of foamed coffee on its surface, similar in appearance to cappuccino coffee. A measured amount of spray-dried instant coffee and a small amount of cold water are combined with vigorous agitation to form a foamed coffee concentrate. Then, hot water is added to make a coffee beverage.
U.S. Pat. No. 4,618,500 to Forquer, incorporated herein by reference, discloses a method for preparing a brewed espresso-type coffee beverage which has a head of froth on the surface of the beverage. Relatively dry steam is injected into the brewed coffee beverage to produce the froth.
U.S. Pat. No. 3,749,378 to Rhodes, incorporated herein by reference, discloses an apparatus for foaming a coffee extract. Gas is introduced into the coffee extract and the foamed coffee is then spray-dried to make a soluble coffee product having a low bulk density.
Although soluble espresso coffee powders are available, there is still a need for a soluble dry espresso coffee composition which, upon reconstitution, exhibits a foam characteristic desired by true espresso connoisseurs. For example, prior resulting espresso beverages lack sufficient foam, the foam dissipates too quickly or there is a combination of both. Accordingly, an instant dry soluble espresso coffee product is desirable which provides foam characteristics of a conventionally made espresso beverage.